4.1.4 Piping
Routing and supporting of the pipelines has been determined based on stress and process calculations. Routing and pipe hangers form a calculated, integral and balanced system. Changing part of this system will cause an altered load distribution, stresses and expansion, which may result in failure or damage.
4.1.5 Safety (Relief) Valves
The purpose of safety (relief) valves is protection of personnel, plant and production. It is a pressure-relieving device for any installation requiring pressure protection; that is, it protects a pressure vessel (or pressure parts) against a pressure in excess of its design strength. The safety (relief) valves relieve the pressure by discharging steam or water when the set pressure is exceeded. Safety (relief) valves are installed on the:
Condensate and feed water system (including deaerator).
Closed cooling water system. HRSG such as, IP economizers, steam drums, super heaters, repeaters.
4.1.6 Steam Silencers
The steam may be released from either low pressure (LP steam vent silencer) of high pressure (HP steam vent silencer) as part of boiler start up system, a bypass vent or a safety relief valve vent system, So it reduce the noise of the expanding steam from the safety (relief) valves and start-up vent valves.
4.1.7 Attemperator
In drum style and once through designs, this is caused by such things as burner orientation and fuel to air ratios. In combined cycle plants, varying gas turbine exhaust temperatures and in the inclusion of duct firing can dramatically affect steam temperatures. In order to ensure the optimum operating heat rate and to protect the steam turbine, the steam temperature in the superheat and reheat sections of the boiler must be controlled. The purpose of the attemperator is cooling the steam, to limit the steam temperature.Fig.(4.7) shows the attemperator location.
4.1.8 Steam Bypass Station
Steam from the outlet of the HP superheater, Re-heater and LP superheater is led to the steam turbine. When the steam turbine is not available the steam is bypassed using a HP bypass station and IP bypass station. HP steam is bypassed to the cold reheat line using the HP bypass station. Reheat steam is bypassed to the condenser using the IP bypass station. If the condenser cannot accept the steam from the IP bypass station, the hot reheat (HRH) steam is dumped to atmosphere using the common HRH blow off. LP steam is not bypassed but will be dumped to the atmosphere using the LP steam blow off if necessary. The bypass stations are equipped with a bypass line for heating the downstream piping preventing thermo-shock.
Routing and supporting of the pipelines has been determined based on stress and process calculations. Routing and pipe hangers form a calculated, integral and balanced system. Changing part of this system will cause an altered load distribution, stresses and expansion, which may result in failure or damage.
4.1.5 Safety (Relief) Valves
The purpose of safety (relief) valves is protection of personnel, plant and production. It is a pressure-relieving device for any installation requiring pressure protection; that is, it protects a pressure vessel (or pressure parts) against a pressure in excess of its design strength. The safety (relief) valves relieve the pressure by discharging steam or water when the set pressure is exceeded. Safety (relief) valves are installed on the:
Condensate and feed water system (including deaerator).
Closed cooling water system. HRSG such as, IP economizers, steam drums, super heaters, repeaters.
4.1.6 Steam Silencers
The steam may be released from either low pressure (LP steam vent silencer) of high pressure (HP steam vent silencer) as part of boiler start up system, a bypass vent or a safety relief valve vent system, So it reduce the noise of the expanding steam from the safety (relief) valves and start-up vent valves.
4.1.7 Attemperator
In drum style and once through designs, this is caused by such things as burner orientation and fuel to air ratios. In combined cycle plants, varying gas turbine exhaust temperatures and in the inclusion of duct firing can dramatically affect steam temperatures. In order to ensure the optimum operating heat rate and to protect the steam turbine, the steam temperature in the superheat and reheat sections of the boiler must be controlled. The purpose of the attemperator is cooling the steam, to limit the steam temperature.Fig.(4.7) shows the attemperator location.
4.1.8 Steam Bypass Station
Steam from the outlet of the HP superheater, Re-heater and LP superheater is led to the steam turbine. When the steam turbine is not available the steam is bypassed using a HP bypass station and IP bypass station. HP steam is bypassed to the cold reheat line using the HP bypass station. Reheat steam is bypassed to the condenser using the IP bypass station. If the condenser cannot accept the steam from the IP bypass station, the hot reheat (HRH) steam is dumped to atmosphere using the common HRH blow off. LP steam is not bypassed but will be dumped to the atmosphere using the LP steam blow off if necessary. The bypass stations are equipped with a bypass line for heating the downstream piping preventing thermo-shock.
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